I bought two Ruger 10/22's early in 2008 new in the box and there was a debate on whether they were making the receiver, barrel clamp, and trigger guard out of plastic. I did the lip test on mine, that is, where metal will feel cold in normal room temperature when I put my lips on it, and plastic feels warm. The components all felt cold to my lips, but slightly warmer than the barrel. Has anyone found evidence that there really was plastic used for those components?
I noticed that the question on the materials seems to have died down since that time.